The power dissipation of integrated circuit chips, and the modules containing the chips, continues to increase in order to achieve increases in processor performance. This trend poses a cooing challenge at both the module and system level. Increased air flow rates are needed to effectively cool high power modules and to limit the temperature of air exhausted into the computer center.
In many large server applications, processors along with their associated electronics (e.g., memory, disk drives, power, etc.) are packaged in removable drawer configurations stacked or aligned within a rack or frame. In other cases, the electronics may be in fixed locations within the rack or frame. Typically, the components are cooled by air moving in parallel air flow paths, usually front-to-back, impelled by one or more air moving devices (e.g., fans or blowers). In some cases it may be possible to handle increased power dissipation within a single drawer by providing greater air flow, for example, through the use of a more powerful air moving device or by increasing the rotational speed (i.e., RPM) of an existing air moving device. However, this approach is becoming unmanageable at the frame level in the context of a computer installation (e.g., data center).
The sensible heat load carried by the air exiting the frame will eventually exceed the ability of room air conditioning to effectively handle the load. This is especially true for large installations of “server farms” or large banks of computer frames close together. In such installations, not only will the room air conditioning be challenged, but the situation may also result in recirculation problems with some fraction of the “hot” air exiting one frame being drawn into the air inlet of the same or a nearby frame. Furthermore, while the acoustic noise level of a powerful (or higher RPM) air moving device in a single drawer may be within acceptable acoustic limits, because of the number of air moving devices in the frame, the total acoustic noise at the frame level may not be acceptable. In addition, the conventional openings in the frame for the entry and exit of air flow make it difficult, if not impossible to provide effective acoustic treatment to reduce the acoustic noise level outside the frame. Finally, as operating frequencies continue to increase, electromagnetic cross talk between tightly spaced computer frames is becoming a problem largely due to the presence of the openings in the covers.
Recently, attempts have been made to address some of the issues noted above by combining air cooling with an air-to-liquid heat exchanger fixed within a server cabinet. Examples of this approach include the systems described in commonly assigned U.S. Pat. Nos. 6,819,563 and 6,775,137, both of which are incorporated herein by reference in their entirety. Notwithstanding these recent air and liquid cooling systems, there remains a need in the art for further improvements to cooling of rack-mounted electronics systems.